A liquid crystal display device has been widely used in a display device that displays high quality images. In a liquid crystal display device, in general, a liquid crystal layer that allows image display based on a predetermined orientation is disposed between a pair of substrates. For the liquid crystal display device, one of factors that determine the image quality is to uniformly maintain the distance between the substrates, that is, the thickness of the liquid crystal layer. Accordingly, spacers are disposed to maintain the thickness of the liquid crystal layer constant. The thickness between the substrates is generally called a “cell thickness” and the cell thickness generally means a thickness of the liquid crystal layer. In other words, the cell thickness means a distance between two electrodes that apply an electric field to a liquid crystal in a display region.
Spacers have been formed conventionally by spreading beads. However, in recent years, spacers with high positional accuracy have been formed from photosensitive resin compositions by photolithography. Spacers formed from photosensitive resin compositions are called “photospacers,”
The photospacer prepared from a photosensitive resin composition through steps of patterning, alkali development and baking tends to be poor in the compression strength of a spacer dot; accordingly, at the time of forming a panel, plastic deformation tends to be large. Therefore, the photospacer, when used in high quality image display, should not have a problem of non-uniformity or image unevenness caused by, for example, a reduction of the liquid crystal layer thickness to below the design value, which in turn caused by the above-mentioned tendency. Furthermore, it is as well important that an alkali development residue of the photosensitive resin composition is not generated in terms of obtaining a higher precision of a liquid crystal display device.
As a display mode of a liquid crystal display device, a TN mode has been adopted (see, for example, Non-patent Document 1). However, the TN mode has a problem in that a viewing angle thereof is narrow. Therefore, a VA mode that is wide in the viewing angle has been proposed (see, for example, Non-patent Document 2).
In the VA mode, the electric field generated between the electrodes is partially tilted by formation of a protrusion having a low dielectric constant, which is called a liquid crystal orientation control protrusion, on one or both of a pair of transparent electrodes disposed up and down, or by patterning of both of the pair of transparent electrodes disposed up and down (see, for example, Non-patent Document 3), whereby multiple domains are formed with respect to the orientation of the liquid crystal, which realizes a display device giving a similar brightness to all viewing angles. Among the VA modes, one that uses a liquid crystal orientation control protrusion is called MVA, ASV, CPA or the like, and one in which both of up and down transparent electrodes are patterned is called PVA.
However, the VA mode is one of display modes where variations in a cell thickness of a liquid crystal cell tend to cause display unevenness. Furthermore, some of other display modes such as an IPS mode and an OCB mode show similar tendencies.
Associated with the above, as a spacer formation technology for maintaining a constant thickness of a liquid crystal layer (cell thickness), it is disclosed to use a resin having an allyl group to form a spacer (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-Open (SP-A) No. 2003-207787
Non-patent Document 1: Yoshihiro, Iwai “Frontier of Liquid Crystal Business,” page 41 (published by Kogyo Chosakai Publishing Inc., 1993)
Non-patent Document 2: “Nikkei Microdevice Additional Volume, Flat Panel Display 2003” (Jitumuhen), pages 82 to 85, published by Nikkei BP Inc.
Non-patent Document 3: “Nikkei Microdevice Additional Volume, Flat Panel Display 2003” (Jitumuhen), page 103, published by Nikkei BP Inc.